Monitoring of water surface area in Lake Qinghai from 1974 to 2016

Abstract

Lake Qinghai, the biggest inland lake and biggest saltwater lake in China, lies in the north-eastern part of the Qinghai Tibet Plateau. The lake is also an important vapour source for the special region. The dynamic variation of its water surface is a response of climate and environment around. In this study the long-time variation of Lake Qinghai was explored from time and space perspectives, based on the shoreline information which was extracted manually with moderate-high spatial resolution remote sensing imagery. The results showed that, as a whole the Lake Qinghai's area decreased from 1974 to 2004 and then increased till 2016. In 2004 the area was smallest, 4223.73 km2, smaller by 253.80 km2 than that in 1974. From 1974 to 1987 the water surface shrank sharply. While the variation range was relatively modest with mean value of 6.85 km2 during the period from 2000 to 2009. During the last 7 years, the water surface increased by 128.27 km2. In 2012, there was a sharp expansion with 65.12 km2 larger than previous year; moreover the annual variation reached maximum, 59.18 km2. The shoreline of Sand island, which lies in the east coast, varied significantly during the past few decades. From 1974 to 2004 the maximum back distance from the coastline was 4.59 km, and the value of annual variation was 0.39 km in 2012. The increase of precipitation in Lake Qinghai region, and the enlarging inflow runoff, which benefited directly from local ecological environment control measures implemented by government, are two important reasons to make the lake expanding in the last two decades.